The invention pertains to a rotational material handling device or grapple of either the mechanical jaw type or magnet type, and has for its objective to improve on the construction and operational efficiency of such device.
The prior patented art contains teachings of rotational grapples in which the grapple jaws are customarily driven directly by a gear motor or by a hydraulic motor coupled with the jaw structure through a planetary transmission, direct spline drive, chain and sprocket gearings, or similar direct drive means.
A serious problem arises with these prior art arrangements particularly where a sudden torque reversal occurs through the drive, as where a rotating load on the grapple strikes a solid abutment. Such accidents frequently cause gear stripping, shaft or key failure and other mechanical damage in the prior art direct drive arrangements.
In contrast to this, the present invention employs a unique and very efficient friction drive for the rotational grapple component through a very simple hydrostatically driven motor wheel which is entirely external to the grapple support and rotational elements for ease of servicing without the need for disassembling the main stationary and rotational telescoping parts of the device. The hydrostatic motor wheel also has a unique floating and self-adjusting suspension which compensates automatically for gradual tire wear. If an abrupt torque reversal should occur through the system, the drive tire merely skids on the rotating plate or flange with which it is frictionally engaged without causing any damage to the device.
The invention also features a downward pressure capability as well as loaded lifting capability through a novel thrust bearing which is interposed between the main stationary and rotational parts of the invention.
Additionally, the invention embodies a simplified, substantially enclosed pressure fluid system for plural grapple jaw operating cylinders including sealed passages through the main rotational sleeve component and the interfitting non-rotational support shaft.
These and other important features which will appear during the course of the following detailed description distinguish the invention structurally and operationally over the known prior art which includes, inter alia, U.S. Pat. Nos. 3,527,495; 3,627,372; 3,759,564; 3,795,421 and 3,877,743.